The disclosures herein relate generally to computer systems and more particularly to portable computers having a sealed hinge clutch.
Portable computers typically include top and base enclosures formed of synthetic, i.e. plastic material. The top and base of most portable computers are attached using a metal hinge clutch to control the torque required to open and close the top. Most portable computers utilize a hinge clutch having either a friction plate design or a friction shaft design. The friction shaft design is often used to minimize the front-to-back dimension of the portable computer. For this type of design, lubrication is necessary to maintain a uniform and consistent pivoting action and clutch torque.
Various hinge devices have been used in computer housings. U.S. Pat. No. 5,566,048 discloses a hinge assembly that allows a display housing to pivot relative to a portable computer base. The hinge assembly has a pivot shaft attached to the display housing and a spring. The spring has two ends. One end is attached to the display housing, and the other end is attached to the base. The spring counteracts the torque created by the weight of the display housing. This allows a smaller and lighter friction mechanism to be used to allow the display housing to remain in an open position at an angular orientation selected by the user.
U.S. Pat. No. 5,142,738 discloses a hinge device used between a rotatable component and a stationary component to work as a pivoting device. The device provides a restrained rotation of one component in relation to the other. The rotational restraint is provided by a high viscosity grease and the torsional force of a coil spring inserted therein in a predetermined angular range to restrain the rotating speed by means of the high viscosity grease and the coil spring.
U.S. Pat. No. 5,001,659 discloses a structure for connecting a cover of a portable laptop personal computer, word processor or similar equipment having a display rotatably connected to a case which accommodates a body of the computer or word processor. The case and cover are electrically interconnected at co-active hinge portions thereof by a pair of deformed O-rings and a pair of flat O-rings.
U.S. Pat. No. 4,730,364 discloses a hinge such as may be used for pivotally attaching a liquid crystal display panel to a portable computer base. The panel is held open in selected angular positions by means of a frictional fit between an O-ring and the end of a bearing which is rotatably retained within a follower, to compress the O-ring between it and the follower such that the frictional resistance between the bearing and the follower may be adjusted to control the holding force on the panel.
Prior hinge clutches do not incorporate a reliable sealing mechanism to contain lubricant within the hinge clutch assembly. As a result, over time, the lubricant has a tendency to migrate from the metal hinge clutch to the plastic housing. Most of the commonly used lubricants deteriorate engineering grade plastics commonly used in computer housings, making them more susceptible to stress cracks.
The loss of lubrication also causes the hinge torque to increase significantly. As the torque required to open and close the computer enclosure increases, the torque loading applied to the adjacent portions of the enclosure also increases. The repeated opening and closing of top of the computer often result in the formation of stress cracks in deteriorated portions of the plastic enclosure.
Accordingly, there is a need for a lubricated hinge clutch that overcomes the shortcomings of prior hinge clutch assemblies so as to avoid contaminating the plastic housing.